Journal of Geosciences, 54 (2009), 1–13

DOI: 10.3190/jgeosci.030

Original paper

Hydrothermal uranium-base metal mineralization of the Jánská
vein, Březové Hory, Příbram, Czech Republic: lead isotopes andchemical dating of uraninite
Pavel Škácha1*, Viktor Goliáš1, Jiří Sejkora2, Jakub Plášil1,2, Ladislav Strnad3, RadekŠkoda4, Josef Ježek5
Institute of Geochemistry, Mineralogy and Mineral Resources, Charles University in Prague, Faculty of Science, Albertov 6,
128 43 Prague 2, Czech Republic; skachap@volny.cz
2
Department of Mineralogy and Petrology, National Museum, Václavské nám. 68, 115 79 Prague 1, Czech Republic
3
Laboratories of Geological Institutes, Charles University in Prague, Faculty of Science, Albertov 6, 128 43 Prague 2, Czech Republic
4
Institute of Earth Sciences, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
5Institute of Applied Mathematics and Information Technologies, Charles University in Prague, Faculty of Science, Albertov 6,
128 43 Prague 2, Czech Republic*
Corresponding author
1

The Jánská vein is one of the important veins of Březové Hory mining district (central Bohemia, Czech Republic). Base
metals were mined here since 14th century and uranium ore during late 1950’s.
Uranium mineralization is younger than most of the base metal mineralization according to macroscopic and microscopic
study. Most specimens of uraninite, obtained from archive, contain more or less abundant galena inclusions. Galena of
this type is non-radiogenic as indicated by its Pb isotopic composition (ICP-MS). Its origin can be explained by remobilisation of the older base-metal mineralization during the younger, uranium-bearing mineralization event. The amountof radiogenic Pb in uraninite fluctuates from 48 up to 89.8 %. The age of theoretical end member of uraninite, calculated
statistically from all measured data (for intersection 208Pb/206Pb = 0), is 269.8 ± 20.3 Ma (2σ). The only uraninite grain
without galena inclusions yielded an age of 263.2 ± 8.9 Ma by chemical dating using electron microprobe. The calculated
age of the uranium mineralization is in agreement with published data for other uranium deposits genetically associatedwith the Central Bohemian Plutonic Complex.
Keywords: uranium, Příbram-Březové Hory, Jánská vein, lead isotopes
Received: 26 March 2008; accepted 14 May 2008; handling editor: E. Jelínek

1. Introduction
The Příbram ore region (central Bohemia, Czech Republic) consists of two ore districts, namely Příbram
uranium-base metal district and the Březové Hory basemetal district. This ore field is the most important Ag–
Pb–Zn–U accumulation in the Bohemian Massif mined
to date having produced in total more than 500,000 t
of lead, 3,500 t of silver and 43,000 t of uranium. The
mining reached depths of 1,500 m in the Březové Horyore district (Prokop shaft) and 1,850 m in the Uranium
district (shaft № 16). General characteristics of the basemetal deposit were summarized by Bambas (1990) anddescription of uranium deposit was given in Arapov etal. (1984). The uranium mineralization manifestations
were relatively rare in the Březové Hory ore district,having been concentrated in several veins only. One ofthe veins, where uranium mineralization was relatively
abundant, is the Jánská vein. It is localized in the centreof the Březové Hory deposit, in the most productive
part of the Březové Hory ore district. The ages of ura-nium mineralization in Příbram ore field available todate are related only to the Uranium district. The main
goal of this article is the presentation of new data on
the isotopic composition of lead in galena and uraninite, as well as their bearing on dating of the primarymineralization in the Březové Hory ore district.

2. Geological setting

2.1. General characteristics of the BřezovéHory ore district
The Březové Hory district and the Uranium district are
spatially related to the exocontact of the Central Bohemian Plutonic Complex (CBPC), which was dated to
338–354 Ma (for literature related to U/Pb zircon datingof CBPC see Holub et al. 1997 and Janoušek et al. 2004).
The 40Ar-39Ar cooling ages (338–352 Ma) of different
plutonic and dyke rocks from the Příbram area (Vrančice,Lešetice and Bohutín) suggest a close temporal relationwww.jgeosci.org

Pavel Škácha, Viktor Goliáš, Jiří Sejkora, Jakub Plášil, Ladislav Strnad, Radek Škoda, Josef Ježek

Fig. 1 Generalized geological setting of the Příbram base metal and uranium districts. Shown are outlines of individual ore deposits as well as the
position of mines (including the Jánská shaft).

between magmatism of the CBPC and the early stages ofthe base-metal mineralization (Žák et al. 1998).
The Březové Hory ore district can be subdivided into
three deposits: central Březové Hory, Černojamské, andBohutín (Fig. 1). The age of beginning of the BřezovéHory ore district exploitation is unknown. Mining at theoutcrops of the veins is documented by archaeological study to the 13th century. The exploitation was very
intense in the whole deposit in the 16th century (Grimm
1856). The attention was focused again on the central
part of mining district in the 18th century, especially for
the Jánská vein. The whole Březové Hory ore district
was intensively mined during the 19th century and theprosperity period finished at the end of the same century.
Mining was unprofitable during most of the 20th century
and it was terminated in 1979.
The hydrothermal veins of the Březové Hory penetrated Neoproterozoic and Cambrian volcanosedimentary
formations. The Cambrian sequence includes greywackes,
sandstones and conglomerates. The sedimentary rocks
were intruded by a swarm of dolerite (“diabase”) dykes
up to several tens of metres wide. Ore veins are often
preferentially localized along these dolerite dykes.
According to relative age of formation, the mineralization is divided into an Early Variscan gold-bearing quartz
period and a Late Variscan base metal period (Bambas
1990; Zachariáš and Stein 2001). The two periods are
separated by an interval of c. 100 Ma, but they often
follow the same structures. The Early Variscan mineralization, which is important for the Bohutín deposit,
was not observed in the Jánská vein. The Late Variscan
mineralization was a single polyascendent mineralization

Hydrothermal uranium mineralization of the Jánská vein (Příbram)process of Early or Late Permian age. The average UPb isotope age of uraninites from the adjacent Uranium
district, belonging to this mineralization, is 265 ± 15 Ma(Legierski 1973) or 275 ± 4 Ma to 278 ± 4 Ma (Anderson
1987). Direct dating of the mineralization in the BřezovéHory ore district is so far missing.
According to the stable isotope and fluid inclusions
studies, the formation temperatures of the Březové Horyore district veins generally range from 150 to 300 ºC.
Fluids were high-saline (15–25 wt. % NaCl eq.) andtheir oxygen was isotopically heavy (δ18O = +6 to +10 ‰SMOW). On the other hand, temperatures of formation
for the nearby Uranium district were lower (80–130 ˚C)and characterized by low salinity (max 5 wt.% NaCleq.) with δ18O ranging between –4 and +6 ‰ SMOW(Žák and Dobeš 1991). This probably points to a distinct
source of the U mineralization.

2.2. Description of the filling and geologic
conditions of the Jánská vein
The Jánská vein is located in Cambrian rocks between the
Anna and Vojtěch shafts in the central Březové Hory ore
deposit. It is one of smaller range veins (it was observed
over a maximal length of about 200 m) in a relatively
dense and involved veins system seen at the surface. The
Janská vein was opened by mining works from surface
down to the 18th level; however it gradually wedges-out
at deeper levels, loosing its economic importance. In thenorthwest its trend is 330° and it gradually swings to
350° behind its crossing with the Václav vein. The dip isrelatively stable at 60–70° to the northeast.
The structure of the Jánská vein can be described as
banded and asymmetric in most cases, less commonly
brecciated. The mineral assemblage does not differ significantly from that of other veins in the Březové Horyore district. Its structure can be described as banded andasymmetric in most cases, less commonly brecciated. It
was observed over a maximal length of c. 200 m. The
vein was mined between the 1st and 18th levels, where it
lost its thickness and economic ore content. Filling contains quartz, barite and carbonates. Main ore minerals are
represented by galena, sphalerite, silver ores, pyrite anduraninite (Fig. 2). According to Babánek (1870), the Jánská
vein belongs to the youngest group of veins in the BřezovéHory deposit. Its apophyses were rich in silver minerals at
the 17th level, especially close to the Clay Fault. The hostrocks are often hydrothermally altered, rock bleaching anda distinct haematitization is evident in the southern parts ofthe vein at the 1st and 2nd levels. A report by Author Collective (1949) described plagioclase pinitization, epidotizationand sericitization in wall rock next to the vein. The Jánská
vein’s width varies much from 1 to 20 cm; in places it evenpasses to a non-mineralized dislocation.

Fig. 2 Sketch of the ore fill in the Jánská vein (Schmidt 1892 modified
by Kirchheimer 1963).

According to Schmidt (1892), uraninite was foundfrom surface down to the 12th level, where the Jánská
vein and Jánská upper vein meet. At this place uraninite
was richly intergrown with pyrargyrite or proustite. At
the 16th level, where the Jánská upper vein branched out,
uraninite was absent.

3. Methods
The X-ray powder diffraction analysis was used for phaseanalysis. To minimize complicated shape of backgrounddue to classic glass sample holder, the samples studied
were placed on the surface of flat silicon wafer mostly inalcoholic suspension. Continuous mode of PANalytical
X´Pert Pro diffractometer with X´Celerator detector wasused for collecting powder diffraction data. It was operated at 40 kV and 30 mA, and secondary monochromator
producing CuKα1,2 radiation was used (X-ray Diffraction Laboratory at Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles
University in Prague). Phase analysis was done using
the search-match algorithm of High-Score program with
PDF-2 database (ICDD 2003).

		Pavel Škácha, Viktor Goliáš, Jiří Sejkora, Jakub Plášil, Ladislav Strnad, Radek Škoda, Josef Ježek

Chemical composition of galena was analysed using
Cameca SX100 electron microprobe (State Geological
Institute of Dionýz Štúr, Bratislava). The analyses were
performed at 20 kV and 20 nA using c. 1 µm beam diameter; counting times were 30–60 s. The following standards were used during the analysis: Ag (Ag); Cd (Cd),As (FeAsS), Sb (Sb2S3); Te (Bi2Te3); Cu, Fe, S (CuFeS2);
Cl (NaCl); Pb (PbS); Bi (Bi), Hg (HgS) and Cl (NaCl).
Chemical composition of uraninite was studied by
Cameca SX100 electron microprobe (Joint Laboratory ofElectron Microscopy and Microanalysis of the Masaryk
University and Czech Geological Survey in Brno). The
operating conditions were as follows: an accelerating
voltage 15 kV, a beam current of 80 nA and a beam dia­meter of 2 µm. Peak counting times were 40–60 s formost minor elements. Uranium was determined on the
U Mβ line (detection limit 270 ppm), thorium on theTh Mα line (detection limit 250 ppm) and Pb on the Pb
Mα line (detection limit 130 ppm). The following standards were used: U – metallic U, Pb – PbSe, Th – ThO2,
P, F – fluorapatite, Y – YAG, La – LaB6, Ce – CeAl2,
Pr – PrF 3, Nd – NdF 3, Sm – SmF 3, Gd – GdF 3, Dy– DyP5O14, Er – YErAG, Yb –YbP5O14, Al – almandine,
Si, Ca, Fe – andradite, Mn – rhodonite, V – vanadinite,S – barite. Data were reduced using the PAP matrix correction routine (Pouchou and Pichoir 1985).
Assuming that the total Pb in uraninite is only radiogenic, i.e. resulting by decay of Th and U, the chemical
age can be calculated using the equation close to published by Montel et al. 1996:
λt
Pb = 238U.03 × 0.99276 × (e 238 -1) × 205.97 + 238U.04
λt× 0.007196 × (e 235 -1) × 206.98 + 232Th.04 × 0.99276 ×
λt(e 232 -1) × 207.97,
where λ238, λ235, and λ232 are decay constants of the 238U,
235
U and 232Th, respectively. Additionally, the concentrations of Pb were manually corrected for Y Lγ2, Th Mζ1and Th Mζ2 overlaps on PbMα. Besides the mentioned
coincidences, the analytical precision of Pb on the Mαline is higher than on Mβ line, where only insignificant
coincidences occur. Lower analytical totals for uraninite
analyses are primarily caused by its porous nature or bya higher oxidation state of uranium (UVI+).
The isotopic data were obtained by ICP-MS (Laboratories of Geological Institutes, Charles University in
Prague). The procedure used for the geological samples
decomposition was similar to Strnad et al. (2005). The
only non-radiogenic Pb isotope is 204Pb, which is normallyused as denominator for reporting isotopic Pb ratios (Faure
1986). This isotope shows a low abundance (c. 4 %) andradiogenic systems contain even less of this isotope. Low
sensitivity and accuracy for determination of isotopic ratios involving 204Pb was the reason, why it was replacedby 208Pb, originating by Th decay. It can be treated as anessentially „non-radiogenic“ isotope because the studiedhydrothermal uraninite does not contain any appreciable
amounts of Th. This was confirmed by our chemical
analyses (EMPA) and by alpha spectroscopy (Jarka 2007).
Thorium, unlike uranium, occurs only in tetravalent state
and under oxidation conditions (at hydrothermal stage)
both elements fractionate from each other.
The 207Pb/206Pb and 208Pb/206Pb isotopic compositions
were determined using a standard configuration of quadrupole-based ICP-MS PQ3 (VG Elemental, UK) equippedwith a water-cooled (~ 4 °C) spray chamber with Meinhard-type nebuliser. The analytical conditions and dataacquisition parameters closely followed those describedin Mihaljevič et al. (2006). The data were acquired in
the peak-jumping mode with 4 points measured per mass
peak and instrument sensitivity at 3 × 104 cps per 1 ng.ml‑1
209
Bi. The total acquisition time was 10 × 30 s. Correction
for the mass bias was performed using NIST SRM 981 (acommon lead isotopic standard) and SRM 982 (an equalatom lead isotopic standard) after every analysed sample
and the time-resolved data were processed off line in a
MS Excel program. The standard errors for measurements of the 207Pb/206Pb and 208Pb/206Pb ratios were below
0.5 % (relative). The accuracy of the measurements wascontrolled by repeated analysis of the AGV-2 standard(USGS, USA; 207Pb/206Pb = 1.2085 ± 0.0006, 208Pb/206Pb= 2.0415 ± 0.0013). Software NCSS (Hintze 2001) wasused for statistical treatment of the isotopic data.

4. Mineralogy and geochemistry of theores

4.1. Ore distribution in the Jánská vein
From the results of field study, examination of an old
mining map from 1760 (private collection) and archive
documents of the uranium survey from the period 1948–
1949 (Author Collective 1949) follows that the uranium
mineralization is concentrated in two ore pillars.
The northern ore pillar, which is located near the
Jánská shaft, is vertical, splays out to the depth and its
position is probably controlled by the Václav vein and
the Clay Fault.
The southern ore pillar, localized in the southeastern partof the Jánská vein, where mining was concentrated during
the period 1948–1949, was dipping c. 35º to the southeast(in a vertical projection of the Jánská vein). Joint occurrenceof uranium and copper mineralization without occurrencesof macroscopic galena (in the area of 1st and 2nd level) is
typical. Longitudinal projection following the Jánská vein
down to the level of 12th horizon was constructed (Fig. 3).
The associated base metal mineralization was minedin 18th century; during the uranium exploration program,Hydrothermal uranium mineralization of the Jánská vein (Příbram)

SE

NW

100 m
Jánská shaft
PetrskéshaftsAnna shaft

CAMBRIAN
U

Cu, U

54,5 kg U
1948

62,4 kg U 1948

Old
workings

U

ora
Barb

250 kg U 1949

U

U

Václav

253 kg U
1949

U

U U

Pb, (Ag), Zn
U

1p.
2p.

t
faul

Cu, U

Cu
U

Clay

Cu

U

3p.

16,4 kg U
1948

5p.

C2 185 kg U
Pb, (Ag), Zn

Longitudinal projectionof the Jánská vein

7p.
Pb, (Ag), Zn

P
R
O
T
E
R
O
Z
O
I
C

8p.
9p.

Pøíbram - Bøezové Hory

30 kg U1949
150 kg U 1949
Pb, (Ag), Zn, U
222 kg U 1948

Jánská upper
vein

10p.
11p.
12p.
13p.

Fig. 3 Longitudinal vertical section of the works at Jánská vein. Original historic mining works for Ag-Pb are marked by light grey colour andstopes of uranium mining with mentioned quantity of the extracted metal from the years 1948–1949 are marked in dark grey.

some remaining ore accumulations and the stope between
11th and 12th levels were mined out. During years 1948
and 1949, in total 1,038.3 kg of uranium was recovered(Author Collective 1949).
Several factors important in localization of uraniumores in the nearby Uranium district were observed. Most
important were lithological, structural, and mineralogicalfactors. In the case of the Jánská vein structural predisposition predominates, as clearly seen in the northern ore
pillar near the Jánská vein (Škácha 2007).

4.2. Principal primary minerals of the Jánská
vein
Galena is the most abundant ore mineral. It forms large
grains and fine-grained aggregates concentrated in several
cm thick veinlets (Galena I). A younger galena generation(Galena II) occurs together with uraninite and is often
overgrown by anglesite in fractures. Although much ofgalena is older then uraninite, younger generation of thebase metal mineralization in the Jánská vein contains
uraninite with microscopic (probably syngenetic) inclusions of galena.
According to chemical analyses (Tab. 1) it is obvious,that galena I does not contain silver. Galena II is younger
than sphalerite and coats its fragments. Both minerals are
in close association with quartz according to the microscopic study (Fig. 4).
Uraninite is the dominant mineral of the uranium
mineralization. It forms black fillings of veinlets up to
2 cm thick and kidney-shaped aggregates with a typicalmetallic lustre, on its own, or less commonly, in association with pyrite (Fig. 5). Larger homogeneous masses ofuraninite show typical semi-metallic lustre and conchoi-		Pavel Škácha, Viktor Goliáš, Jiří Sejkora, Jakub Plášil, Ladislav Strnad, Radek Škoda, Josef Ježek

Tab. 1 Electron-microprobe analyses of galena from the uranium mineralization (Galena I, sample 15J_1) in wt. % and apfu
Pb
Ag
Sb
Bi
Te
Fe
S
Cl
total
Fe
Pb
Ag
Sb
Bi
Te
S
Cl

1
85.89
<0.01
0.09
<0.01
0.10
0.04
13.25
0.05
99.41
0.002
0.997
0.000
0.002
0.000
0.002
0.994
0.003

2
84.91
<0.01
<0.01
0.24
0.03
0.02
12.96
0.06
98.21
0.001
1.003
0.000
0.000
0.003
0.001
0.989
0.004

Fig. 5 Botryoidal uraninite (“pitchblende”) aggregates up to 2 cm
overgrown by younger pyrite from the 15th level of the Jánská vein(collections of the Mining Museum in Příbram, coll. No 853). Photoby P. Škácha.

Sum of cations and anions = 2 apfu

dal fracture. Weathered uraninite-bearing veinlets containpowdery uraninite aggregates. Some uraninite samples
enclose galena. These samples come from an ore pillar
in surroundings of the Jánská shaft. The genesis of thisgalena is probably related to remobilisation by younger
uranium mineralization. Our microprobe study showedthat this type of galena occurs in discrete zones of uraninite and individual galena grains are tiny, only severalµm across (Fig. 6). Minor occurrences of uraninite fromthe southern ore pillar come from places where copper
minerals surround uraninite and galena has not been deFig. 6 BSE image of uraninite with light, finely disseminated grains andveinlets of non-radiogenic galena (sample J_1). Photo width 1.2 mm.
Photo by J. Sejkora and P. Škácha.

Fig. 4 Polished section from 2nd level of the Jánská vein in reflected
light. Light gray sphalerite is overgrown by white galena. Both phases
are younger than dark gray quartz. Photo width 1 mm. (photo by J.
Sejkora and P. Škácha).



tected. This uraninite does not contain galena detectable
by XRD, but ICP-MS established increased amounts of
non-radiogenic Pb. This indicates that the galena presence can be also expected at this locality.
Table 2 shows chemical composition of uraninitefrom the Jánská vein. The increased contents of Ca 2+
can be according to Janezcek and Ewing (1992) explained by a 2U 4+ ↔ U 6+ + Ca 2+ substitution. The
other possibility is that the content of Ca is caused bysubmicroscopic carbonates inclusions, but it was notconfirmed by the EMPA study. The content of Pb 2+
corresponds to radiogenic Pb and, in part, to common
lead in submicroscopic galena inclusions. Empiricalformula of uraninite from the Jánská vein, based on

Hydrothermal uranium mineralization of the Jánská vein (Příbram)Tab. 2 Electron-microprobe analyses of uraninite (in wt. % and apfu)
SiO2
UO2
Al2O3
V 2O 3
As2O3
Y 2O 3
Ce2O3
Nd2O3
Sm2O3
Gd2O3
Dy2O3
Er2O3
Yb2O3
CaO
MnO
FeO
PbO
total
Si4+
U4+
Al3+
V3+
As3+
Y3+
Ce3+
Nd3+
Sm3+
Gd3+
Dy3+
Er3+
Yb3+
Ca2+
Mn2+
Fe2+
Pb2+

2J5_8
1.78
83.30
0.20
0.07
0.33
0.23
0.11
0.08
0.01
0.03
0.43
0.00
0.01
3.46
1.34
0.65
4.47
96.48
0.064
0.668
0.008
0.002
0.007
0.004
0.001
0.001
0.000
0.000
0.005
0.000
0.000
0.134
0.041
0.019
0.043

2J5_8
1.44
81.80
0.15
0.04
0.43
0.22
0.10
0.05
0.02
0.05
0.40
0.02
0.02
3.45
1.29
0.68
5.15
95.30
0.053
0.669
0.006
0.001
0.010
0.004
0.001
0.001
0.000
0.001
0.005
0.000
0.000
0.136
0.040
0.021
0.051

2J5_8
1.39
82.55
0.14
0.08
0.44
0.14
0.04
0.05
0.03
0.01
0.30
0.02
0.00
3.75
0.96
0.53
5.00
95.42
0.051
0.678
0.006
0.002
0.010
0.003
0.000
0.001
0.000
0.000
0.004
0.000
0.000
0.148
0.030
0.016
0.050

2J5_8
1.63
81.77
0.18
0.04
0.42
0.22
0.09
0.04
0.00
0.04
0.35
0.03
0.00
3.84
1.20
0.62
5.09
95.54
0.059
0.658
0.008
0.001
0.009
0.004
0.001
0.001
0.000
0.001
0.004
0.000
0.000
0.149
0.037
0.019
0.050

2J5_8
1.72
82.27
0.19
0.01
0.42
0.22
0.08
0.13
0.01
0.05
0.44
0.02
0.05
3.50
1.30
0.66
4.63
95.68
0.062
0.665
0.008
0.000
0.009
0.004
0.001
0.002
0.000
0.001
0.005
0.000
0.001
0.136
0.040
0.020
0.045

J_15
1.32
78.06
0.08
0.74
0.16
0.03
0.00
0.00
0.02
0.02
0.40
0.00
0.00
3.88
1.47
0.86
7.22
94.26
0.047
0.627
0.004
0.021
0.004
0.001
0.000
0.000
0.000
0.000
0.005
0.000
0.000
0.150
0.045
0.026
0.070

J_15
1.21
79.88
0.07
0.73
0.18
0.05
0.00
0.00
0.00
0.00
0.42
0.00
0.00
3.92
1.57
0.81
6.03
94.87
0.044
0.640
0.003
0.021
0.004
0.001
0.000
0.000
0.000
0.000
0.005
0.000
0.000
0.151
0.048
0.024
0.058

J_15
1.41
79.94
0.06
0.78
0.17
0.04
0.00
0.00
0.00
0.00
0.41
0.01
0.00
4.00
1.55
0.84
5.51
94.72
0.051
0.637
0.002
0.022
0.004
0.001
0.000
0.000
0.000
0.000
0.005
0.000
0.000
0.153
0.047
0.025
0.053

J_1
1.62
81.98
0.14
0.05
0.21
0.73
0.20
0.17
0.06
0.13
0.51
0.06
0.05
3.60
1.60
0.79
2.92
94.80
0.059
0.660
0.006
0.001
0.005
0.014
0.003
0.002
0.001
0.001
0.006
0.001
0.001
0.140
0.049
0.024
0.028

J_1
1.61
84.02
0.12
0.09
0.17
0.52
0.19
0.13
0.02
0.07
0.40
0.05
0.00
3.39
1.38
0.62
3.04
95.82
0.059
0.684
0.005
0.003
0.004
0.010
0.003
0.002
0.000
0.001
0.005
0.001
0.000
0.133
0.043
0.019
0.030

J_1
1.84
83.83
0.15
0.09
0.21
0.47
0.13
0.13
0.03
0.07
0.49
0.05
0.00
3.51
1.46
0.54
3.00
95.99
0.066
0.674
0.006
0.003
0.005
0.009
0.002
0.002
0.000
0.001
0.006
0.001
0.000
0.136
0.045
0.016
0.029

J_1
1.64
83.92
0.13
0.10
0.21
0.47
0.15
0.07
0.02
0.10
0.47
0.03
0.00
3.51
1.45
0.56
3.00
95.81
0.060
0.680
0.005
0.003
0.005
0.009
0.002
0.001
0.000
0.001
0.006
0.000
0.000
0.137
0.045
0.017
0.029

Sum of cations = 1 apfu

Janeczek and Ewing (1992), is (mean of 12 analyses,
based on sum of cations + Si = 1 apfu): (U0.66REE3+0.01
M3+0.02M2+0.25)Σ0.94(SiO4)0.06O1.58.
According to Collective of Authors (1949) occurrencesof uranium blacks (“sooty pitchblende”) were recordedin the upper levels of the Jánská vein. We could verify
this only in the southern ore pillar. After Jarka (2007) it
contains 6.3 wt. % U (alpha spectroscopy). The XRD
study resulted in determination of an amorphous phaseaccompanied by chlorite.
Barite occurs frequently in the northern ore pillar as
veinlets composed of tabular grains and as imperfecttabular crystals up to 1 cm in cavities. It is found in association with uraninite and base metal minerals at the 1st

and 2nd levels. A younger barite generation occurs rarely
with silver ores and uranium mineralization at the 2ndlevel of the Prokop mine.
Calcite is a common mineral in the museum specimensfrom the Jánská vein. It forms massive aggregates ofbrown colour, often surrounding uraninite. It has not beenfound at presently accessible parts of the Jánská vein,
except for rare recently-formed small crystals depositedon manganese oxides.
Quartz is the most common gangue mineral at the upper levels of the deposit. It forms mainly massive veinlet
filling of grey or reddish colour and rare crystals to 1
cm. In proximity to uranium minerals this quartz turns
grey to black.

Pavel Škácha, Viktor Goliáš, Jiří Sejkora, Jakub Plášil, Ladislav Strnad, Radek Škoda, Josef Ježek

most likely end members, galena and theoretical uraninite end-member, we can calculate the amount of purely
radiogenic lead (Tab. 3). In the studied set of uraninite
samples the fraction of radiogenic lead varies from 48.0
to 89.8 %. This means that relatively small amount of
non-radiogenic galena is sufficient for observed shifts inlead isotope compositions.

5. Lead isotopic composition of galena
and uraninite
The 208Pb/206Pb versus 207Pb/206Pb diagram (Fig. 7) wasconstructed from newly obtained data (Tab. 3). We
added the following standard recommended values to thediagram: SRM 981 – Common Lead Isotopic Standard,
SRM 982 – Equal Atom Lead Isotopic Standard, SRM
983 – Radiogenic Lead Isotopic Standard and measured
values for Proterozoic uraninite standard CRM6-A(“Pitchblende ore”).
The studied galena specimens from all of the BřezovéHory ore deposits are isotopically homogeneous within
analytical 2σ errors (Fig. 7). Isotopic composition of
uraninites from the Jánská vein varies within a broad
range. Our data show that local uraninite contains a large
amount of lead, which did not originate by U decay. On
the contrary, the Pb isotopic composition of uraninites
can be explained as mixture with syngenetic galena. This
alternative is proved by the presence of minute galena
inclusions in uraninite. From the compositions of the

5.1. 207Pb/206Pb lead isotope dating
Due to the non-radiogenic lead admixture (contained ingalena inclusions), the isotope analyses of uraninite forma linear array in Fig. 7. A pure uraninite has not beenfound, but its lead isotope composition could have been
extrapolated by linear regression. One end member of thisrelation is formed by three points represented by galenasfrom the Jánská vein. These galenas are isotopicallyhomogeneous within the measurement errors. Anotherend member (uraninite) was obtained at the intersection
point of regression function with x axis (208Pb/206Pb = 0)
(Fig. 7).

2.50
2,140
2.140

Pb / 206Pb

2,130
2.130

Galena“common lead”
SRM 981
Protiklonná v.

2,120
2.120

2.00

2,110
2.110

Jánská v.

2,090
2.090

Jánská v.
Klementská v.

1.50

207

Pb /

206

Primary minerals

ine

2,080
2.080
0,852
0,854
0,856
0,858
0,860
0,862
0,864
0,866
0,868
0,870
0.852
0.856
0.860
0.868
0.864

l
ion

Standards

s

res

reg

Pb
Uraninite + galena

208

0.040
0,040

1.00
Uraninite + galena
Uraninite + galena

SRM 982 0.035
0,035“equal atom lead”

Pb / 206Pb

Pb / 206Pb

208

2,100
2.100

GalenaJánská v.

Vojtìšská v.

Uraninite
Uraninite + galena
Uraninite + galena

0.50

CRM6-A

0.00
0.00

208

Uraninite + galena
Uraninite
Uraninite + galena

0.030
0,030
0.025
0,025
0.020
0,020
0.015
0,015
4.49 * 10-4
0.010
0,010
0.005
0,005
269.8
350
0.000
0,000
0,050
0,052
0,054
0.050
0.054

“radiogennic lead”
SRM 983

0.10

0.20

confidence
bonds 1Age (Ma)
450
550
0,056

0,058
0.058

650
0,060

CRM
6-A

0,062
0.060

207

Pb / 206Pb

0.30

0.40

0.50
207

Pb /

0.60
206

0.70

0.80

0.90

1.00

Pb

Fig. 7 Diagram 208Pb/206Pb versus 207Pb/206Pb for analyses of uraninite and galena from the Jánská vein with the position of theoretical radiogenic
end-member (uraninite) and common lead end-member (galena). Linear fit to the data, enlarged area of the galena cluster, and intercept of theregression line with x axis (expressed also as time axis) are also shown.

0.36450.24410.25140.24050.1344
0.46200.19820.28010.38540.47350.2535borytroidal pitchblende, between 3 and 5 level (PR) N 856
borytroidal pitchblende, 8th level (PR) No 855
borytroidal pitchblende, 15th level (PR) No 853
massive uraninite with galena, unknown level (PF) No 449
veinstuff with uraninite and galena, 13th level (VSB) No P107
veinstuff with uraninite and galena, 13th level (VSB) No 2711
veinstuff with uraninite and galena, 13th level (VSB) No 2712
veinstuff with uraninite and galena, 13th level (VSB) No 2713
veinstuff with uraninite and galena, 13th level (VSB) No 2714
veinstuff with uraninite and galena, 13th level (VSB) No 3053
veinstuff with uraninite and galena, 13th level (VSB) No 3055

4J_1

8J_1

15J_1

J_1

J_10

J_11

J_12

J_13

J_14

J_15

J_17

uraninite (+galena)1)

uraninite (+galena)1)

uraninite (+galena)1)

1)

uraninite (+galena)1)

uraninite (+galena)1)

uraninite (+galena)1)

uraninite (+galena)1)

uraninite (+galena)1)

0.862410.051640.06212

calculated Jánská vein, arithmetic mean of 1J1_9, 2J2_12 and 2J3_1 samples

calculated Jánská vein, calculated theoretical end member, free of galena

CRM 6-A “Pitchblende Ore” Proterozoic, New Brunswick Laboratory

uraniniteuraninite (standard)

0.8596

galena0.8583

galena, Vojtěch mine, vein Protiklonná, 5th level (PR) No 495

J_4

galena, Vojtěch mine, main Vojtěch vein, 24 level (PR) N 1505

J_3

0.000140.00045n.a.

0.00240.00550.00320.00380.00220.00180.00080.00130.00130.00070.00060.00140.00040.02850.02010.02570.01670.00100.0006

2.1126

2.10932.1035

2.10932.10162.10390.5232

1.09280.86210.59350.37751.06050.21430.49420.51660.50590.81050.65170.3416

Pb/206Pb

0.002540.00000

2.10495

208

0.00004

n.a.

n.a.

0.00720.02580.01410.00790.00370.00830.00140.00210.00320.00160.00060.00310.00070.00440.00920.00690.00970.00120.0010

1σ
207

98.7

100

0

0.35

0.51

0.17

-0.29

-0.05

0.34

75.1

48.0

58.8

71.8

81.9

49.4

89.8

76.7

75.4

76.3

61.4

69.0

83.9

Pb/206Pb

208

99.9

100

0

-0.36

-0.21

0.07

-0.21

0.16

0.05

75.1

48.1

59.0

71.8

82.1

49.6

89.8

76.5

75.5

76.0

61.5

69.0

83.8

Pb/206Pb

radiogenic lead calc. (%)

The composition of the theoretical radiogenic (uraninite) end member was extrapolated from the whole dataset, its isotopic 207Pb/206Pb age is 269.8 ± 20.3 Ma.

Shown are measured lead isotope ratios and calculated proportions of radiogenic lead in at. %.

Sources of studied samples: (NF): New finding, (PR): Collection of Mining museum, Příbram-Březové Hory, (PF): Mineralogical collection of Faculty of Science, Charles University in Prague,(VSB): Pošepný collection, VŠB–Technical University of Ostrava.

ogalenath

galena0.8610fine-grained galena, Štěpán mine, vein Klement, 2nd level (PR) No 1247

J_2

galena0.86482 cm vein of galena, Jánská vein, 2nd level (NF)

2J3_1

0.8628galena0.8596veinlets of galena in quartz gangue, Jánská vein, 2 nd level (NF)

2J2_12

galenathin veinlet of galena in quartz gangue, Jánská vein, 1 st level (NF)

1J1_9

XRD detected

galena1)uraninite (+galena)uraninite (+galena)uraninite (+galena)1)

o

1)

th

0.3033fragments in tectonic breccia, 2nd level, south (NF)

2J5_10rd

0.1825fragments in tectonic breccia, 2nd level, south (NF)

2J5_8

uraninite

1σlead isotope ratios (measured)Pb/206Pb

uraninite

207

samplemineraldescription

Tab. 3 Lead isotopic composition of the studied samples of uraninite and galena from Jánská and the other veins (ICP-MS)

Hydrothermal uranium mineralization of the Jánská vein (Příbram)		Pavel Škácha, Viktor Goliáš, Jiří Sejkora, Jakub Plášil, Ladislav Strnad, Radek Škoda, Josef Ježek

The age of the theoretical uraninite end member canbe calculated following Faure (1986) as:
207	    206

235

Pb
1
eλ U*t - 1=* λ238U*t
Pb 137.8 e-1(1)

where the ratio 207Pb/206Pb corresponds to the x-interceptof a straight line fitting data in Fig. 7, λ238 and λ235 aredecay constants for 238U and 235U, respectively.
Using software NCSS we found the best-fit line to ourdata in the form 208Pb/206Pb = 2.595147 * 207Pb/206Pb 0.134218 with standard error of the y-intercept 0.000607.
The x-intercept is calculated dividing the y-intercept byslope, yielding the theoretical pure uraninite end-member’s 207Pb/206Pb = 0.051719. This corresponds to an age
270.7 ± 26.9 Ma.
Nevertheless, such an approach does not take into account the errors of 208Pb/206Pb and 207Pb/206Pb ratios forindividual data points. To solve this problem, we useda non-linear least squares inverse method of Tarantola
and Valette (1982), which we implemented into Matlab
software. The advantage of the method is that the equation (1) can be involved in the inversion as a constraining
condition. The resulting age was similar to that obtainedby the classical regression, but with a smaller error: 269.8± 20.3 Ma.

5.2.	Chemical dating of uraninite
On the basis of ICP–MS analyses, the chemical age ofseveral uraninite specimens was determined. However, an
unrealistically high lead amount was found in Variscan
uraninites. In the light of isotopic data, microscopic and
X-ray diffraction study of the specimens, the increased
content of lead is explained by the presence of galena
inclusions of non-radiogenic origin (Fig. 6).
In a single case (sample J_1), an inclusion-free area
in polished section has been found (Tab. 2, anal. J_1-1– J_1-4). But the influence of common lead in the bulk
J_1 sample is evident (according to ICP-MS), like in theother uraninites (Tab. 3, anal. 2J5_8 and J_15). Consequently, an average chemical age for the inclusion-freearea was calculated at 263.2 ± 8.9 Ma (uncertainty of age
determination is expressed as 2σ, Tab. 4).

6. Discussion
The uranium mineralization occurrences on the Jánská
vein are very interesting in respect to the evolution of
the whole Březové Hory base metal deposit. According toknown data and new observations, the Jánská vein filling
resulted from a polyphase mineralization process.
10

A particularly intriguing question represents thegenesis of galena inclusions present in all studied specimens of uraninite from the Jánská vein. Analogous typeof galena, usually considered as being of radiogenic
origin, was also found in other deposits worldwide, e. g.
at Oklo deposit of Proterozoic age (Evins et al. 2005).
Few uraninite grains with galena accounting for even up
to 40 vol. % were found in the Oklo deposit (Janezcek1999). However, origin of the galena inclusions by U
decay was not confirmed by our ICP-MS data, whichshow that the galena inclusions have isotopic composition resembling the primary galena. The distributionof inclusions is uneven; their accumulations in certain
zones of uraninite may suggest hydrothermal systempulsation. This galena could be related to a partial destruction of an older base metal mineralization by fluids
associated with uranium mineralization. Non-radiogenic
galena inclusions in uraninite are probably present insome other deposits, even though it cannot be provenwithout the isotope evidence (Löfvendhal and Åberg
1981). For instance, minute inclusions of remobilized
Pb sulphoselenides were reported by Golubev et al.
(2002) from outer zone of younger pitchblende at theSchlema–Alberoda deposit. Radiogenic origin of Pb wasisotopically confirmed but no galena inclusions werementioned by these authors.
Patočka et al. (1984) presented a review and re-interpretation of Pb isotope results from the Czech ore
deposits measured by Legierski (1971, 1973), Bernard
et al. (1979) and others. In this review were included
two analyses of galena from Březové Hory and Bohutín.
Our isotope data for galena from Jánská and other veinsare very similar and illustrate homogenous source of
non-radiogenic lead. On other hand our isotope andchemical age data (269.8 ± 20.3 Ma and 263.2 ± 8.9 Ma)
for Březové Hory uraninite are very close or the same,
within the error, compared to these previously publisheddata for the nearby Příbram uranium ore district: 265 ±15 Ma (Legierski 1973) or 275 ± 4 Ma to 278 ± 4 Ma(Anderson 1987).
The genesis of the Příbram hydrothermal base metal
and uranium deposits is spatially related to the exocontactof the Central Bohemian Plutonic Complex. The oldest
recognized mineralization is quartz – Au-bearing, early
Variscan stage, temporary related to the crystallizationof the youngest phases of the plutonic complex. Someplutonic dykes are younger than the Au-bearing quartz
veinlets as documented in Libčice near Nový Knín for
instance by Slavík (1914) and Zoubek (1942). A newer
dating was performed for early Variscan gold-bearing
deposits (Zachariáš and Stein 2001): Petráčkova Hora
(Re-Os molybdenite 342.1–348.5 Ma), Mokrsko (Re-Os
molybdenite 342.9 ± 1.4 Ma), Kasejovice (Re-Os molybdenite 338.5 ± 1.3 Ma) and Jílové u Prahy (40Ar-39Ar

Hydrothermal uranium mineralization of the Jánská vein (Příbram)Tab 4 Chemical age of uraninite from the Jánská vein, calculated from
EMPA analyses
Chemical Age (Ma)sample J_1

262 ± 15265 ± 15263 ± 15263 ± 15

corrected (for Y and Th) average age

263.2 ± 8.9

standard age error is expressed as 2σ.

muscovite 338.6 ± 0.5, 339 ± 0.6 Ma). It indicates that
this mineralization stage overlapped, or followed shortly
after, crystallization of the main granitoids in the Central
Bohemian Plutonic Complex.
Base metal mineralization is younger than the quartz– gold-bearing mineralization. It can be deduced fromthe gangue relationships of a vein filling (e.g. in Bohutíndeposit). There are numerous unpublished observationsin this respect, kept in the Archive of DIAMO Enterprise;some of these data were summarized by Arapov et al.
(1984). The U-Pb ages of 265–278 Ma (Legierski 1973)
and 275 ± 4 to 278 ± 4 Ma (Anderson 1987) characterize
the nearby uranium deposits. Similar ages were obtainedby the K-Ar method for the Rožná uranium deposit inwestern Moravia: 277.2 ± 5.5 and 264 ± 4.3 Ma (Kříbek
and Hájek 2005). Comparable data yielded samples fromother deposits in the Bohemian Massif, including those inGermany (Golubev et al. 2002). Permian ages of the older
uranium mineralization are typical of the French Massif Central as well as of the whole European Variscides(Marignac and Cuney 1999).
A younger mineralization process dated at 150–190
Ma (Arapov 1984; Golubev et al. 2002; Kříbek et al.
2003) seems important in relatively peripheral areas of
the Bohemian Massif only (Krušné hory Mts., Bohemian
Forest and Rožná–Olší deposits). Recrystallization andalteration of uraninite to coffinite is typical of this late
process. This indicates a post-Variscan–early Alpine(Jurassic?) reactivation and rejuvenation of fault zones
in the Bohemian Massif.

7. Conclusions
The uranium mineralization occurs in two ore pillars
on the Jánská vein. Joint occurrence of base metal anduranium mineralizations is typical of the northern ore
pillar. On the other hand, in the southern ore pillar uranium mineralization is associated with Cu mineralization.
Uraninite is the dominant primary uranium phase on the

Jánská vein; base metal mineralization is represented bygalena, sphalerite and pyrite. The most abundant gangueminerals are quartz, barite and minor calcite.
According to our isotopic data and microscopic study,
uraninite always contains some proportion of non-radiogenic galena. It represents remobilized galena in theform of minute inclusions. The theoretical radiogenic(uraninite) end-member’s Pb isotopic composition was
extrapolated, corresponding to a 207Pb/206Pb age of 269.8± 20.3 Ma. In addition, it was possible to determine
chemical age for one sample of uraninite (263.2 ± 8.9Ma). The data obtained by both methods are in a good
agreement.
According to macroscopic and microscopic observations, base metal mineralization of the Jánská vein isolder than the dated uranium mineralization. However,the field relations indicate relatively close genetic relations between the older base metal and the superimposeduranium mineralizations.
The age of uranium mineralization presented in thisreport is in good agreement with data published for otherlate Variscan hydrothermal uranium deposits.
Acknowledgments. The authors gratefully acknowledge
cooperation of M. Fayadová, P. Jarka, J. Zachariáš and O.
Šebek (Faculty of Science, Charles University in Prague,
Prague), D. Ozdín (State Geological Institute of Dionýz
Štúr, Bratislava), colleagues who kindly provided samples from museum collections, namely M. Duraj (VŠB
– Technical University of Ostrava), P. Kašpar (Charles
University in Prague), E. Litochlebová (Mining Museum,Příbram) and of the DIAMO Enterprise, namely J. Kovář
and K. Škvor, for support in course of this project. This
work was financially supported by the Grant Agencyof the Academy of Science (No KJB – 301110602) andby Ministry of Education of the Czech Republic (MSM
0021620855).

References
Anderson EB (1987) Isotopic–geochronological investigation of the uranium deposits of Czechoslovakia. (MS)Czechoslovak Uranium Industry Report 1862-87, pp
1–32 (in Russian)Arapov JA, Bojcov VJ, Česnokov NI, Djakonov AV,
Halbrštát J, Jakovjenko AM, Kolek M, Komínek J,
Kozyrev VN, Kremčukov GA, Lažanský M, Milovanov IA, Nový V, Šorf F (1984) Czechoslovak uranium
deposits. ČSUP Příbram, pp 1–368 (in Czech)
Author Collective (1949) The Jáchymov mines enterprisecalculation of resources for year 1948. Unpublishedmanuscript, DIAMO SUL, Příbram (in Russian)11

Pavel Škácha, Viktor Goliáš, Jiří Sejkora, Jakub Plášil, Ladislav Strnad, Radek Škoda, Josef Ježek

Babánek F (1870) Die Gangverhältnisse der Anna–Neuprocopigrube am Birkenberge bei Przibram. Öster Zeitschrift f Berg u Hüttenwessen 18: 25–37
Bambas J (1990) The Březové Hory ore deposit. Příbram,
pp 1–200 (in Czech)
Bernard J, Legierski J, Šmejkal V (1979) Isotopic investigation of ore paragenesis in the Bohemian Massif.
Unpublished manuscript, Geofond, Prague, pp 1–87
Evins LZ, Jensen KA, Ewing RC (2005) Uraninite recrystallization and Pb loss in the Oklo and Bangombé natural
fission reactors, Gabon. Geochim Cosmochim Acta 69:
1589–1606
Faure G (1986) Principles of Isotope Geology. Second edition. John Willey & Sons, New York, pp 1–589
Golubev VN, Chernyshev IV, Velichkin VI, Cuney M,
Poty B. (2002) Isotopic constraints on the age at theSchlema–Alberoda uranium deposit (Erzgebirge). In:Kříbek B, Zeman J (eds) Uranium deposits – From Their
Genesis to Their Environmental Aspects. Czech Geological Survey, Prague, pp 57–60
Grimm J (1856) Die Erzniederlage bei Přibram in Böhmen.
Berg Hüttenm Jahrb 5: 93–168
Hintze J (2001) NCSS and PASS. Number Cruncher Statistical Systems. Kaysville, Utah, http://www.ncss.com/
Holub FV, Cocherie A, Rossi P (1997) Radiometric datingof granitic rocks from the Central Bohemian Plutonic
Complex (Czech Republic): constrains on the chronologyof thermal and tectonic events along the MoldanubianBarrandian boundary. C R Acad Sci IIA 325: 19–26
ICDD (2003) PDF-2 database, ICDD, Newton Square,
PA, USA
Janeczek J, Ewing RC (1992) Structural formula of uraninite. J Nucl Mater 190: 128–132
Janeczek J (1999) Mineralogy and geochemistry of natural
fission reactors in Gabon. In: Burns PC, Finch R (eds)
Uranium: Mineralogy, Geochemistry and the Environment. Mineralogical Society of America Reviews in
Mineralogy 38: pp 321–392
Janoušek V, Braithwaite CJR, Bowes DR, Gerdes A (2004)
Magma-mixing in the genesis of Hercynian calc-alkaline
granitoids: an integrated petrographic and geochemical
study of the Sázava intrusion, Central Bohemian Pluton,
Czech Republic. Lithos 78: 67–99
Jarka P (2007) Uranium-base metal mineralization of the
Jánská vein, Příbram-Březové Hory, Czech Republic:
alpha spectrometric determination of the radionuclides.
Unpublished MSc. thesis. Faculty of Science, Charles
University in Prague, pp 1–45 (in Czech)
Kirchheimer F (1963) Uran und seine geschichte. E. Schweizerbartsche Verlagsbuchhandlung, Stuttgart, pp 1–372
Kříbek B, Žák K, Spangenberg J, Jehlička J, Prokeš S,
Komínek J (2003) Bitumens in the late Variscan hydro-

12

thermal vein-type uranium deposit of Příbram, Czech
Republic: sources, radiation-induced alteration, and relation to mineralization. Econ Geol 94: 1093–1114Kříbek B, Hájek A, (eds) (2005) Rožná uranium deposit:
model of late Variscan and post Variscan mineralizations.
Czech Geological Survey, Prague, pp 1–98 (in Czech)
Legierski J (1971) Pb-Pb, U-Pb, U-Th-Pb methods andtheir application on the ore deposits. Unpublished PhD.
thesis, Faculty of Science, Charles University in Prague,
pp 1–145 (in Czech)
Legierski J (1973) Model ages and isotopic compositionof ore leads of the Bohemian massif. Čas Min Geol 18:
1–23 (in Czech)
Löfvendhal R, Åberg G (1981) An isotope study of Swedish secondary U-Pb minerals. Geol Fören i Stockholm
Förhand 103: 331–342
Marignac C, Cuney M (1999) Ore deposits of the French
Massif Central: insight into the metallogenesis of the
Variscan collision belt. Miner Depos 34: 472–504
Mihaljevič M, Zuna M, Ettler V, Šebek O, Strnad L,
Goliáš V (2006) Lead fluxes, isotopic and concentration
profiles in a peat deposit near a lead smelter (Příbram,
Czech Republic). Sci Total Environ 372: 334–344
Montel JM, Foret S, Veschambre M, Nicollet C, Provost
A (1996) Electron microprobe dating of monazite. Chem
Geol 131: 37–53
Patočka F, Pošmourný K, Rajlich P, Richter A, Vaněček
M (1984) Pb isotopic data utilization for prospection
in volcanosedimentary areas of the Bohemian Massif.
Czech Geological Survey, Prague, pp 1–84 (in Czech)
Pouchou JL, Pichoir F (1985) “PAP” procedure for improved quantitative microanalysis. Microbeam Anal
20: 104–105
Schmidt J (1892) Montan-geologische Beschreibung desPříbramer Bergbau – Terrains und der Verhältnisse in der
Grube. K.k. Hof und Stadtdruckerei, Wien, pp 1–62
Slavík F (1914) Die Goldquartzgänge Mittelböhmens.
Z prakt Geol Lagerstättenkde 22: 343–373
Strnad L, Mihaljevič M, Šebek O (2005) Laser ablation andsolution ICP-MS determination of REE in USGS BIR1G, BHVO-2G and BCR-2G glass reference materials.
Geostand Geoanal Res 29: 303–314Škácha P (2007) Characterization of the uranium-polymetallic
mineralization of the Jánská vein and redistribution of leadisotopes into the secondary phases, Příbram-Březové Hory,
Czech Republic. Unpublished MSc. thesis. Faculty of Science, Charles University in Prague, pp 1–41 (in Czech)
Tarantola A, Valette B (1982) Generalized nonlinear
inverse problems solved using the least squares criterion.
Rev Geophys Space Phys 20: 219–232
Zachariáš J, Stein H (2001) Re-Os ages of Variscanhydrothermal gold mineralisations, Central BohemianHydrothermal uranium mineralization of the Jánská vein (Příbram)

metallogenetic zone, Czech Republic. In: Piestrzyński
et al. (eds): Mineral Deposits at the Beginning of the
21st Century, Swets & Zeitlinger Publishers, Lisse, pp851–854
Zoubek V (1942) Geologisches Gutachten über das Liebschitzer–Borotitzer goldführende Gebiet. Unpublishedmanuscript, Geofond, Prague pp 1–15

Žák K, Dobeš P (1991) Stable isotopes and fluid inclusions
in hydrothermal deposits: the Příbram ore region. Rozpr
ČSAV: 1–109
Žák K, Vlašímský P, Lawrence W. Snee (1998) 40Ar/39Ar cooling ages of selected rocks of the Příbram ore region and thequestion of timing of sulfidic hydrothermal mineralization.
Zpr geol výzk za Rok 1997, pp 172–173 (in Czech)

Hydrotermální uran-polymetalická mineralizace Jánské žíly, Březové Hory, Příbram, ČR:izotopy Pb a chemické datování uraninitu
Jánská žíla je jednou z významných žil březohorského ložiska. Od 14. stol. zde byly dobývány polymetalické rudya krátce také na konci 50. let 20. stol. i rudy uranové. V rámci předkládané práce byl studován především archivní
vzorkový materiál. Uranová mineralizace je mladší než větší část mineralizace polymetalické, což bylo prokázáno
jak makrostrukturním, tak i mikroskopickým studiem. Většina vzorků uraninitu obsahuje více či méně galenitových
inkluzí. Tento galenit je podle výsledků ICP-MS analýz neradiogenní. Jeho vznik je pravděpodobně spojen s remobilizací galenitu mladší uranovou mineralizací. Koncentrace radiogenního olova v uraninitu kolísají od 48,0 do 89,8
rel. %. Stáří teoretického krajního členu uraninitu, které bylo statisticky spočítáno z celého souboru naměřených dat(pro průsečík 208Pb/206Pb = 0), činí 269,8 ± 20,3 Ma. Bylo nalezeno jediné zrno uraninitu lokálně bez inkluzí galenitu,
které bylo použito pro datování pomocí vlnově-disperzní elektronové mikroanalýzy. Získané chemické stáří uranové mineralizace, 263,2 ± 8,9 Ma, dobře odpovídá publikovaným údajům pro ostatní hydrotermální uranová ložiska
Českého masívu.

13